Variable gain amplifier circuit, method of correcting DC offset of the variable gain amplifying circuit, and radio receiving apparatus
AssigneeNEC Electronics Corporation
InventorHideo Ohba
Life of this patent
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Abstract
A variable gain amplifier circuit according to an embodiment of the invention includes: an output offset correcting unit for executing correction to attenuate a fixed offset component independent of a gain change of a variable gain amplifier circuit out of a DC offset involved in an output voltage of an amplifying unit; and an input offset correcting unit for executing correction to attenuate an input offset component that varies depending on a gain of an amplifying unit. The correction of the fixed offset component with the output offset correcting unit and the correction of the input offset component with the input offset correcting unit are independently executed.
Claims27
A variable gain amplifier circuit, comprising:
- an amplifying unit capable of switching a gain;
- and
- a correction control unit that individually executes correction to attenuate a fixed offset component independent of a change in gain of the amplifying unit out of a DC offset involved in an output voltage of the amplifying unit and correction to attenuate an input offset component that varies depending on the gain of the amplifying unit,
- wherein the fixed offset component is corrected while setting the gain of the amplifying unit such that the input offset component is not involved in the output voltage of the amplifying unit.
A DC offset correcting method for attenuating a DC offset involved in an output voltage of a differential amplifier circuit capable of switching a gain, comprising:
- executing correction to attenuate a fixed offset component independent of a change in gain of the differential amplifier circuit out of the DC offset;
- and
- executing correction to attenuate an input offset component that varies depending on the change in gain of the differential amplifier circuit,
- wherein the fixed offset component is corrected while setting the gain of the differential amplifier circuit such that the input offset component is not involved in the output voltage of the differential amplifier circuit.
A radio receiving apparatus, comprising:
- a receiving unit for receiving a radio signal and outputting a baseband signal;
- a variable gain amplifier circuit for amplifying the baseband signal output from the receiving unit;
- an A/D converter for converging the baseband signal amplified with the variable gain amplifier circuit into a digital signal;
- and
- a digital signal processing circuit for processing the digital signal,
- the variable gain amplifier circuit comprising a correction control unit for independently executing correction to attenuate a fixed offset component independent of a gain change of the variable gain amplifier circuit out of a DC offset involved in an output signal of the variable gain amplifier circuit, and executing correction to attenuate an input offset component that varies depending on the gain of the amplifying unit,
- wherein the fixed offset component is corrected while setting the gain of the amplifying unit such that the input offset component is not involved in the output voltage of the amplifying unit.
A DC offset correcting method for attenuating a DC offset involved in an output voltage of a differential amplifier circuit capable of switching a gain, comprising:
- calculating a fixed offset component VOS_fix independent of a gain change of the differential amplifier circuit and an input offset component VOS_in that varies depending on a gain of the differential amplifier circuit based on output offsets VOS(A1) and VOS(A2) provided that VOS(A1) and VOS(A2) represent an output offset for a first gain A1 of the differential amplifier circuit and an output offset for a second gain A2 of the differential amplifier circuit;
- and
- executing correction to attenuate the fixed offset component VOS_fix and the input offset component VOS_in,
- wherein the fixed offset component VOS_fix and the input offset component VOS_in are derived from two expressions:
- VOS(A1)=VOS_in*A1+VOS_fix
- VOS(A2)=VOS_in*A2+VOS_fix.
Dependencies are inferred from the claim text.